Bosma effect | Francesco Sylos Labini

Title: The Tully-Fisher relation and the Bosma effect

Journal: Monthly Notices of the Royal Astronomical Society, Volume 527, Issue 2, January 2024, Pages 2697–2717, https://doi.org/10.1093/mnras/stad3278

Authors: Francesco Sylos Labini, Giordano De Marzo, Matteo Straccamore, and Sébastien Comerón

In this paper, Sylos Labini and collaborators introduce the dark matter disk model, which provides a new interpretation of the dynamics of disk galaxies. The motivation behind this model stems from the observed inconsistency between the observed flat rotation curves of spiral galaxies and the expected Keplerian decline based on the luminous matter in the galactic disk. Traditionally, this discrepancy has led to the conclusion that massive spherical dark halos dominate the gravitational dynamics of spiral galaxies.

Continue reading →

Francesco Sylos Labini, Giordano De Marzo, Matteo Straccamore, Sébastien Comerón

Monthly Notices of the Royal Astronomical Society, Volume 527, Issue 2, January 2024, Pages 2697–2717, https://doi.org/10.1093/mnras/stad3278

(https://arxiv.org/abs/2310.15673)

We show that the rotation curves of 16 nearby disc galaxies in the THINGS sample and the Milky Way can be described by the NFW halo model and by the Bosma effect at approximately the same level of accuracy. The latter effect suggests that the behavior of the rotation curve at large radii is determined by the rescaled gas component and thus that dark matter and gas distributions are tightly correlated. By focusing on galaxies with exponential decay in their gas surface density, we can normalize their rotation curves to match the exponential thin disc model at large enough radii. This normalization assumes that the galaxy mass is estimated consistently within this model, assuming a thin disc structure. We show that this rescaling allows us to derive a new version of the Tully-Fisher (TF) relation, the Bosma TF relation that nicely fit the data. In the framework of this model, the connection between the Bosma Tully-Fisher (TF) relation and the baryonic TF relation can be established by considering an additional empirical relation between the baryonic mass and the total mass of the disc, as measured in the data.